An unmanned aerial vehicle (UAV), also referred to as an unmanned drone or drone, is an aircraft that does not carry a human operator and is remotely piloted by an external operator on the ground. The typical UAVs are usually deployed for military/civil special operation applications such as policing, scientific research or inspection of security dangers, etc.
In consideration of various factors such as flight duration, positioning accuracy and signaling distance, it may be desirable to permit the typical UAVs to fly only within a confined scope. Accordingly, several methods have been developed to initiate a return flight towards the operator when the UAV is at or near a boundary of the confined scope. For example, when it is detected that the distance from the UAV to the operator is equal to or greater than a predetermined threshold, a control instruction may be generated automatically to instruct the UAV to fly to the operator. For such conventional methods, the flight direction of the return flight of the UAV may not change during the return flight because the position of the operator may be considered as a fixed position. However, it frequently happens that the operator moves around during the return flight of the UAV, for example, the operator may be in a car or on a train. Thus, the UAV is not be able to track the position change of the operator in some conditions, and therefore can not accurately fly back to the operator.
Thus, there is a need for further improvement of the UAVs.